Growth promotion is a crucial issue for farm and breeding specialists, who mainly seek to optimize the production of healthy animals before slaughter or for research purposes. Such a concern should lead them to use growth promoting products that would prove beneficial to the animals and also to humans, in the case of meat-producing animals.
One major caveat in farms and breeding environments is the weight loss, slow growth rate along with a recrudescence of concomitant diseases, drug cost, and mortality which lead to a decrease in animal yields and ultimately to considerable economic losses. In this connection, post-weaning or post-hatching animals are particularly vulnerable to agents impeding growth.
Infections caused by either non-hygienic conditions or close proximity between animals, for example, are among the most common factors leading to the above-mentioned caveat.
One conventional solution used to alleviate this problem has been to use antibiotic growth promoters in feeds. However, use of antibiotic growth promoters is also highly controversial because, as is well known, even at sub-therapeutic doses, continued antibiotic use can lead to selection of antibiotic-resistant bacterial strains in the treated animals (Arnold S et al.; Wegener H C et al. and Schwarz S et al.). In fact, in the last ten years, there has been an emergence of more pathogenic and more antibiotic-resistant Escherichia coli strains and/or husbandry changes (early weaning) and/or new European regulations forbidding use of antimicrobial agents as growth promoters or for prophylaxis treatment (prevention of diseases) and use of high levels of heavy metals, such as zinc oxide in the feed. The weaning period is particularly associated with higher antibiotic use during animal production.
Consequently, there is now a growing resistance to the use of antibiotic growth promoters and heavy metals due to recrudescence of antibiotic resistance, allergic reactions to antibiotic residues, and contamination of cultivated soil.
Another caveat that farm and breeding specialists also have to face is growth heterogeneity among herds of animals. More specifically, in a purpose of optimized meat production for example, farmers seek to produce consistent herds of animals displaying the most homogeneous growth rate possible before slaughter, to avoid increased costs. However, animals generally present different rates of growth and different vulnerabilities to infectious agents, among others.
There is thus a constant need for innovating agents that promote growth of animals and that advantageously further contribute to homogenize and optimize animal growth.